In liquid crystal display devices, phase-difference films are widely used for compensating the phase-difference caused by birefringence of the liquid crystal cell. Many phase-difference films with a variety of configurations have been hitherto proposed. From the viewpoint of productivity and cost efficiency, stretched films are widely used as the phase-difference films that are produced by causing orientation of a transparent resin by stretching to exhibit birefringence. Examples of such stretched films may include films made of triacetylcellulose, which are advantageous in costs and productivity, and films made of polycarbonate resins, which have a good heat resistance. Recently, phase-difference films that contain polymers having alicyclic structures are drawing attention because of good heat resistant, low moisture absorption, and low photoelasticity properties.
However, the stretched alicyclic polymer-containing phase-difference films do not always exhibit a sufficient level of adhesiveness (adhesion strength) to polarizers, particularly those made of polyvinyl alcohol (PVA), compared to phase-difference films made of conventionally used materials.
To solve the aforementioned problem, a variety of efforts have been made. For example, surface treatments such as corona treatment are conducted on the surface of the phase-difference films or modifications are made to compositions of adhesive agents. Despite these efforts, satisfying results have not been obtained. According to the studies by the inventors, the aforementioned insufficiency in adhesion strength is due to cohesive fracture that occurs in a part near the top surface of the film. When a film that contains a polymer having an alicyclic structure as the main component is stretched to form a phase-difference film, the polymers are oriented and the molecular entanglements are reduced, thereby causing such cohesive fracture.
However, birefringence caused by molecular orientation is an essential property for a phase-difference film. Thus, it has been difficult to secure cohesive fracture durability while exhibiting birefringence. Addressing to this issue, e.g., Patent Literature 1 discloses a technique in which a certain solvent is applied onto a surface of a film that has been oriented by stretching so that the orientation on the film surface is relaxed and the adhesiveness of the film to the polarizer is improved.